It's not easy. It starts with parts that cost around $400. Then Patel and his partner, Deva Seetharam, have to write code to run on the tiny Linux-based computer that he's hoping will serve as the brains of his new phone.

So why bother? After all, it's not like cell phones are hard to find or terribly expensive.

Patel says he has lost patience with even the slimmest Motorolas and most advanced Nokias. He has been trying to build new features for cell phones for years, and he--like a growing number of other impatient developers--has concluded that phones have to be as flexible as ordinary computers if he's going to make progress.

"I want the phone to be much more open," Patel said. "The world's best research and development lab is all the hackers out there. Enable them, and they'll do it."

Thirty years ago, this could have been Apple Computer co-founder Steve Wozniak or any of his peers in their garages, building "homebrewed" computers without any inkling of the impending PC explosion. But the mobile world is in a way the inverse of that curve: Cell phone use has already exploded all over the world, but it is only recently that falling component prices have made it practical for homebrew phone hackers to build their own.

Certainly, the phone tinkerers are chafing at the boundaries set by the handset makers and the big phone carriers. They want phones to be programmable, so they can create their own services, either as start-up companies or just for their own use.

"The world's best research and development lab is all the hackers out there. Enable them, and they'll do it."

Patel, who studied at the Massachusetts Institute of Technology's Media Lab for several years before moving to U.K.-based carrier Orange, and ultimately to his own start-up, on Monday talked with CNET News.com about melding social applications like LinkedIn or MySpace with a phone's address book.

That type of service, which connects sprawling lists of people into overlapping groups of "friends," and allows visitors to see who is online or active, would be a much better model for a cell phone's lists of contacts, he said. But today's cell phones are virtually impossible to tweak in that way.

Casey Halverson, a Seattle-based mobile developer who is also working on homemade phone projects, has similar complaints. Commercial cell phones don't let developers write at a basic level that talks directly to the hardware, which makes some programming tasks impossible or hugely inefficient, he said.

"I think as more people move to mobile devices, they will be running into more and more limits with closed systems," Halverson said. "For now, this kind of project is limited to tinkerers, but in the future there might be some kind of open platform for people to do these kinds of things."

Challenge to carriers' power?
None of this is likely to become mainstream soon. In a market increasingly filled with cheap phones that take pictures, play music and show television reruns, a make-your-own kit isn't likely to turn many heads outside the Radio Shack crowd.

But innovations that happen at the technological fringe have a way of filtering into the mainstream over time. The first Apple computer created by Wozniak and Steve Jobs set the foundation for a desktop computer revolution. The wonky dial-up bulletin board systems of the 1980s evolved into today's near-universal Internet access. Peer-to-peer programs developed in dorm rooms transformed the biggest media companies in the world.

"I think as more people move to mobile devices, they will be running into more and more limits with closed systems."

--Casey Halverson, mobile developer

A generation of cell phones that are as open and programmable as computers could be unpopular with cell phone companies, which have relied on control of their networks and the associated phones to keep people paying subscription fees. The music industry likes the idea of selling songs over phones, for example, in part because the tight control of networks makes piracy more difficult.

For the most part, this hardware-hacker activity hasn't yet come to the attention of the big carriers. A spokesman for Cingular Wireless stressed that any cell phone radio has to be approved by the Federal Communications Commission and the carrier itself before using the network, but said that the company supported experimentation.

"We do encourage competition and innovation in the marketplace," Cingular spokesman Clay Owen said. "It's great for people to experiment, given the right regulatory approvals."

Today, the phone hackers are largely in the prototype stage, keeping track of their progress and looking for ideas from the community on their blogs. (Patel and Seetharam's blog is here, and Halverson's is here.)
Most aren't starting entirely from scratch. To comply with regulatory requirements, the projects have to find radio components that have already been approved by the FCC.

In this vein, tinkerers have found several companies that sell components originally meant for embedded systems such as surveillance cameras or GPS (Global Positioning System) receivers, which are allowed to transmit on the big cell phone networks.

Once all of those parts are connected, a homebrew phone needs a Subscriber Identification Module, or SIM, card, the little chip that stores information about which carrier network to use, what the phone's number is, and other personal data. These can be taken out of any GSM (Global System for Mobile Communications)-based phone, or can be purchased on a prepaid basis.

Cingular Wireless and T-Mobile phones both use the GSM wireless standard in the United States. Other carriers use a different technology, which makes it harder for the tinkerers to adapt their equipment.

The early phone tinkerers are hoping that their work sparks a broader response in the open-source community. Once a few people show a way forward in hardware, interesting things can be done by other software developers, they say.

"I have very selfish goals," Patel said. "I want to create demos and prototypes to show clients, and I can't demonstrate the future to you if I can't actually access it. But it's very clear that it's the hacker kids that are doing all the cool stuff."